1. Field of the Invention
The present invention relates to a light emitting diode (LED) module, and more particularly to an LED module including a composite reflector formed with diffraction lines through which light can be diffused.
The LED module of the present invention diffuses light over a wide area rather than focuses light on a narrow area, achieving improved luminance uniformity. The LED module of the present invention is particularly suitable for use in a backlight unit for a television.
2. Description of the Related Art
A general backlight unit reflects light using a reflection mechanism but distributes light over a narrow area and does not disperse light due to the rectilinear propagation of light, resulting in non-uniform luminance
To solve such problems, some backlight units provided with diffraction gratings are known. Such a backlight unit includes a light guide plate having fine diffraction patterns formed on the upper or lower surface thereof and light sources arranged at one lateral side of the light guide plate to disperse light.
White light emitted from the light sources enters through one lateral side of the light guide plate and propagates inside the light guide plate by total reflection. For example, the light guide plate is made of a material with high transmittance.
A portion of the light incident on the upper surface of the light guide plate is diffracted by the diffraction patterns formed on the upper surface of the light guide plate. The diffracted light is emitted through the upper surface of the light guide plate and is uniformly diffused by a diffusion plate to illuminate a flat panel display.
The conventional backlight unit suffers from the inconvenience that the diffusion plate designed to diffuse the light emitted from the light guide plate requires the use of a light collecting plate for converting the diffused light into front light.
When white light is emitted from the upper surface of the light guide plate through the diffraction patterns, color dispersion occurs, which is explained by the fact that refractive index and transmittance vary depending on the wavelength of light. That is, since the angle of emission of the light emitted from the diffraction patterns is determined by the wavelength of the light, color separation is caused when the diffraction patterns have the same pitch.